Diagnosis of Hypokalemia
Mahmoud Barazi, M.D.
Nephrology Fellow
TTUHSC
Case
• 77 y.o WF who presented with a chief
complain of Diarrhea.
• Also found to have Hypokalemia and
Hypomagnesaemia.
• HPI:
- 7 days hx of diarrhea with decreased oral
intake.
- No F/C/S
Case
• PMH
- Non-Hodgkin’s lyphoma S/P Autologus BMT
- HTN
- AKD
- CHF
Case
• Home Medications:
- ASA 81 mg daily
- Lasix 20 mg daily
- Robitussin 20 mEq p.o BID
- Tylenol 650 mg PO q4h prn
- Folic Acid 1 mg po bid
- Loratadine 10 mg po daily
Physical Exam
• VS: Tmp 99 HR 94 BP 101/51 RR 16 SaO2 92%
Gen: A&O x 3, in mild distress
HEENT: AT/NC, EOMI, PERRLA
Neck: Supple, No JVD, No thyromegaly
Chest: CTAB
CVS: S1, S2 normal, No M/R/G, NSR
ABD: Soft, NT, BS present, No organomegaly
EXT: No C/C/E
Labs @ presentation
• WBC
6.2 Hgb 11.3 Plt 60
• Na 137
K 2.1
Cl 95
CO2 28
AG 16
Glu 101 BUN 18 Cr 1.1
Ca 7.8
Alb 3.2
Mg 1.4
• UA pH 6.5
Trace Protein Positive Nitrite
Moderated Leuk. Esterase Spec Gravity
1.009 Cloudy
RBC 0-3 WBC 15-2
• C-Diff neg. Urine culture was positive for E.coli
Causes of Hypokalemia
• Decreased K Intake
• Increased entry into cells
-
Elevation in pH
Increased Insulin
Elevated B-agonist activity
Hypokalemic periodic paralysis
Marked increase in blood cell production
Hypothermia
Chlorquine intoxication
Causes of Hypokalemia
• Increased GI losses
-
Vomiting
Diarrhea
Tube drainage
Laxative abuse
Causes of Hypokalemia
• Increased urinary losses
- Diuretics
- Primary mineralocorticoid excess
- Loss of gastric secretions
- Nonreabsorable anions
- Metabolic acidosis
- Hypomagnesaemia
- Amphotericin B
- Salt-wasting nephropathies – including Batter’s or
Gitelman’s syndrome
- Polyuria
Diagnosis of Hypokalemia
• Can usually be determined from the history
• In other case, the diagnosis is not readily
apparent
• Measurement of BP, urinary K exertion and
assessment of AB balance are often helpful
Urinary Response
Urinary Response
Urinary response
• The minimum urine K concentration in
response to Hypokalemia is 5 to 15 meq/L
• A normal subject can lower urinary potassium
exertion below 25 to 30 meq per day in the
presence of potassium depletion.
• < 15 meq per day is likely representative of
extrarenal losses
Acid Base Assessment
• Metabolic Acidosis
- with Low urine K exertion in asymptomatic
patient is suggestive of Lower GI losses due to
Laxative abuse or villous adenoma
- with K wasting is most often due to DKA,
Type 1 or Type 2 RTA
Acid Base Assessment
• Metabolic Alkalosis:
- With low Urine K exertion is due to surreptitious
vomiting or diuretic use
- With K wasting and normal BP is most often due to
surreptitious vomiting or diuretic use or to Batter’s
syndrome. Urine pH and Urine Cl concentration are
helpful
- With K wasting and HTN is suggestive of surreptitious
diuretic Rx in Pts with underlying HTN, renovascular
disease or primary mineralocorticoid excess
Bartter’s & Gitelman’s Syndrome
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Autosomal recessive disorders
Hypokalemia
Metabolic Alkalosis
Hyperreninemia
Hyperplasia of juxtaglomular apparatus
Hyperaldosteronism
Occasionally hypomagnesaemia
Bartter’s Syndrome
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Named after Dr. Frederic Bartter
Prevalence 1 per million
Often, but not always associated with MR
Pt with a variant of classic Bartter’s syndrome
suffer from the same electrolytes disorders,
but also has sensorineural deafness and renal
failure
Gitelman’s Syndrome
• After Dr. Hillel Gitelman
• Prevalence is 1 per 40000
• More benign than Bartter’s
Distinctions between Batter’s &
Gitelman’s Syndrome
Bartter’s Syndrome
Gitelman’s Syndrome
Localization of defect
Ascending limb of Hanle
Distal Tubule
Age of Presentation
Prenatal, during infancy,
early childhood
Mostly late childhood or at
adult age
Biochemical difference
Serum Mg may be
decreased
Serum Mg is decreased
Urinary exertion of Ca is
increased
Urinary exertion of Ca
reduced
Concentrating capacity
severely impaired
Concentrating capacity
normal or slightly impaired
GFR may be normal or
declining
GFR is normal
Functional Studies
Back to our Pt
• Day 4 of hospitalization
Mg 1.6
K in 24 hour urine was 57 and Ca was 32
• Day 9 of hospitalization
Mg 1.8
K in 24 hour urine was 81 and Ca was 52
Diagnosis
?